blk-map.c

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    1 /*
    2  * Functions related to mapping data to requests
    3  */
    4 #include <linux/kernel.h>
    5 #include <linux/module.h>
    6 #include <linux/bio.h>
    7 #include <linux/blkdev.h>
    8 #include <scsi/sg.h>            /* for struct sg_iovec */
    9 
   10 #include "blk.h"
   11 
   12 int blk_rq_append_bio(struct request_queue *q, struct request *rq,
   13                       struct bio *bio)
   14 {
   15         if (!rq->bio)
   16                 blk_rq_bio_prep(q, rq, bio);
   17         else if (!ll_back_merge_fn(q, rq, bio))
   18                 return -EINVAL;
   19         else {
   20                 rq->biotail->bi_next = bio;
   21                 rq->biotail = bio;
   22 
   23                 rq->__data_len += bio->bi_size;
   24         }
   25         return 0;
   26 }
   27 
   28 static int __blk_rq_unmap_user(struct bio *bio)
   29 {
   30         int ret = 0;
   31 
   32         if (bio) {
   33                 if (bio_flagged(bio, BIO_USER_MAPPED))
   34                         bio_unmap_user(bio);
   35                 else
   36                         ret = bio_uncopy_user(bio);
   37         }
   38 
   39         return ret;
   40 }
   41 
   42 static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
   43                              struct rq_map_data *map_data, void __user *ubuf,
   44                              unsigned int len, gfp_t gfp_mask)
   45 {
   46         unsigned long uaddr;
   47         struct bio *bio, *orig_bio;
   48         int reading, ret;
   49 
   50         reading = rq_data_dir(rq) == READ;
   51 
   52         /*
   53          * if alignment requirement is satisfied, map in user pages for
   54          * direct dma. else, set up kernel bounce buffers
   55          */
   56         uaddr = (unsigned long) ubuf;
   57         if (blk_rq_aligned(q, uaddr, len) && !map_data)
   58                 bio = bio_map_user(q, NULL, uaddr, len, reading, gfp_mask);
   59         else
   60                 bio = bio_copy_user(q, map_data, uaddr, len, reading, gfp_mask);
   61 
   62         if (IS_ERR(bio))
   63                 return PTR_ERR(bio);
   64 
   65         if (map_data && map_data->null_mapped)
   66                 bio->bi_flags |= (1 << BIO_NULL_MAPPED);
   67 
   68         orig_bio = bio;
   69         blk_queue_bounce(q, &bio);
   70 
   71         /*
   72          * We link the bounce buffer in and could have to traverse it
   73          * later so we have to get a ref to prevent it from being freed
   74          */
   75         bio_get(bio);
   76 
   77         ret = blk_rq_append_bio(q, rq, bio);
   78         if (!ret)
   79                 return bio->bi_size;
   80 
   81         /* if it was boucned we must call the end io function */
   82         bio_endio(bio, 0);
   83         __blk_rq_unmap_user(orig_bio);
   84         bio_put(bio);
   85         return ret;
   86 }
   87 
   88 /**
   89  * blk_rq_map_user - map user data to a request, for REQ_TYPE_BLOCK_PC usage
   90  * @q:          request queue where request should be inserted
   91  * @rq:         request structure to fill
   92  * @map_data:   pointer to the rq_map_data holding pages (if necessary)
   93  * @ubuf:       the user buffer
   94  * @len:        length of user data
   95  * @gfp_mask:   memory allocation flags
   96  *
   97  * Description:
   98  *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
   99  *    a kernel bounce buffer is used.
  100  *
  101  *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
  102  *    still in process context.
  103  *
  104  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
  105  *    before being submitted to the device, as pages mapped may be out of
  106  *    reach. It's the callers responsibility to make sure this happens. The
  107  *    original bio must be passed back in to blk_rq_unmap_user() for proper
  108  *    unmapping.
  109  */
  110 int blk_rq_map_user(struct request_queue *q, struct request *rq,
  111                     struct rq_map_data *map_data, void __user *ubuf,
  112                     unsigned long len, gfp_t gfp_mask)
  113 {
  114         unsigned long bytes_read = 0;
  115         struct bio *bio = NULL;
  116         int ret;
  117 
  118         if (len > (queue_max_hw_sectors(q) << 9))
  119                 return -EINVAL;
  120         if (!len)
  121                 return -EINVAL;
  122 
  123         if (!ubuf && (!map_data || !map_data->null_mapped))
  124                 return -EINVAL;
  125 
  126         while (bytes_read != len) {
  127                 unsigned long map_len, end, start;
  128 
  129                 map_len = min_t(unsigned long, len - bytes_read, BIO_MAX_SIZE);
  130                 end = ((unsigned long)ubuf + map_len + PAGE_SIZE - 1)
  131                                                                 >> PAGE_SHIFT;
  132                 start = (unsigned long)ubuf >> PAGE_SHIFT;
  133 
  134                 /*
  135                  * A bad offset could cause us to require BIO_MAX_PAGES + 1
  136                  * pages. If this happens we just lower the requested
  137                  * mapping len by a page so that we can fit
  138                  */
  139                 if (end - start > BIO_MAX_PAGES)
  140                         map_len -= PAGE_SIZE;
  141 
  142                 ret = __blk_rq_map_user(q, rq, map_data, ubuf, map_len,
  143                                         gfp_mask);
  144                 if (ret < 0)
  145                         goto unmap_rq;
  146                 if (!bio)
  147                         bio = rq->bio;
  148                 bytes_read += ret;
  149                 ubuf += ret;
  150 
  151                 if (map_data)
  152                         map_data->offset += ret;
  153         }
  154 
  155         if (!bio_flagged(bio, BIO_USER_MAPPED))
  156                 rq->cmd_flags |= REQ_COPY_USER;
  157 
  158         rq->buffer = NULL;
  159         return 0;
  160 unmap_rq:
  161         blk_rq_unmap_user(bio);
  162         rq->bio = NULL;
  163         return ret;
  164 }
  165 EXPORT_SYMBOL(blk_rq_map_user);
  166 
  167 /**
  168  * blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage
  169  * @q:          request queue where request should be inserted
  170  * @rq:         request to map data to
  171  * @map_data:   pointer to the rq_map_data holding pages (if necessary)
  172  * @iov:        pointer to the iovec
  173  * @iov_count:  number of elements in the iovec
  174  * @len:        I/O byte count
  175  * @gfp_mask:   memory allocation flags
  176  *
  177  * Description:
  178  *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
  179  *    a kernel bounce buffer is used.
  180  *
  181  *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
  182  *    still in process context.
  183  *
  184  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
  185  *    before being submitted to the device, as pages mapped may be out of
  186  *    reach. It's the callers responsibility to make sure this happens. The
  187  *    original bio must be passed back in to blk_rq_unmap_user() for proper
  188  *    unmapping.
  189  */
  190 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
  191                         struct rq_map_data *map_data, struct sg_iovec *iov,
  192                         int iov_count, unsigned int len, gfp_t gfp_mask)
  193 {
  194         struct bio *bio;
  195         int i, read = rq_data_dir(rq) == READ;
  196         int unaligned = 0;
  197 
  198         if (!iov || iov_count <= 0)
  199                 return -EINVAL;
  200 
  201         for (i = 0; i < iov_count; i++) {
  202                 unsigned long uaddr = (unsigned long)iov[i].iov_base;
  203 
  204                 if (!iov[i].iov_len)
  205                         return -EINVAL;
  206 
  207                 /*
  208                  * Keep going so we check length of all segments
  209                  */
  210                 if (uaddr & queue_dma_alignment(q))
  211                         unaligned = 1;
  212         }
  213 
  214         if (unaligned || (q->dma_pad_mask & len) || map_data)
  215                 bio = bio_copy_user_iov(q, map_data, iov, iov_count, read,
  216                                         gfp_mask);
  217         else
  218                 bio = bio_map_user_iov(q, NULL, iov, iov_count, read, gfp_mask);
  219 
  220         if (IS_ERR(bio))
  221                 return PTR_ERR(bio);
  222 
  223         if (bio->bi_size != len) {
  224                 /*
  225                  * Grab an extra reference to this bio, as bio_unmap_user()
  226                  * expects to be able to drop it twice as it happens on the
  227                  * normal IO completion path
  228                  */
  229                 bio_get(bio);
  230                 bio_endio(bio, 0);
  231                 __blk_rq_unmap_user(bio);
  232                 return -EINVAL;
  233         }
  234 
  235         if (!bio_flagged(bio, BIO_USER_MAPPED))
  236                 rq->cmd_flags |= REQ_COPY_USER;
  237 
  238         blk_queue_bounce(q, &bio);
  239         bio_get(bio);
  240         blk_rq_bio_prep(q, rq, bio);
  241         rq->buffer = NULL;
  242         return 0;
  243 }
  244 EXPORT_SYMBOL(blk_rq_map_user_iov);
  245 
  246 /**
  247  * blk_rq_unmap_user - unmap a request with user data
  248  * @bio:               start of bio list
  249  *
  250  * Description:
  251  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
  252  *    supply the original rq->bio from the blk_rq_map_user() return, since
  253  *    the I/O completion may have changed rq->bio.
  254  */
  255 int blk_rq_unmap_user(struct bio *bio)
  256 {
  257         struct bio *mapped_bio;
  258         int ret = 0, ret2;
  259 
  260         while (bio) {
  261                 mapped_bio = bio;
  262                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
  263                         mapped_bio = bio->bi_private;
  264 
  265                 ret2 = __blk_rq_unmap_user(mapped_bio);
  266                 if (ret2 && !ret)
  267                         ret = ret2;
  268 
  269                 mapped_bio = bio;
  270                 bio = bio->bi_next;
  271                 bio_put(mapped_bio);
  272         }
  273 
  274         return ret;
  275 }
  276 EXPORT_SYMBOL(blk_rq_unmap_user);
  277 
  278 /**
  279  * blk_rq_map_kern - map kernel data to a request, for REQ_TYPE_BLOCK_PC usage
  280  * @q:          request queue where request should be inserted
  281  * @rq:         request to fill
  282  * @kbuf:       the kernel buffer
  283  * @len:        length of user data
  284  * @gfp_mask:   memory allocation flags
  285  *
  286  * Description:
  287  *    Data will be mapped directly if possible. Otherwise a bounce
  288  *    buffer is used. Can be called multple times to append multple
  289  *    buffers.
  290  */
  291 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
  292                     unsigned int len, gfp_t gfp_mask)
  293 {
  294         int reading = rq_data_dir(rq) == READ;
  295         unsigned long addr = (unsigned long) kbuf;
  296         int do_copy = 0;
  297         struct bio *bio;
  298         int ret;
  299 
  300         if (len > (queue_max_hw_sectors(q) << 9))
  301                 return -EINVAL;
  302         if (!len || !kbuf)
  303                 return -EINVAL;
  304 
  305         do_copy = !blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf);
  306         if (do_copy)
  307                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
  308         else
  309                 bio = bio_map_kern(q, kbuf, len, gfp_mask);
  310 
  311         if (IS_ERR(bio))
  312                 return PTR_ERR(bio);
  313 
  314         if (!reading)
  315                 bio->bi_rw |= REQ_WRITE;
  316 
  317         if (do_copy)
  318                 rq->cmd_flags |= REQ_COPY_USER;
  319 
  320         ret = blk_rq_append_bio(q, rq, bio);
  321         if (unlikely(ret)) {
  322                 /* request is too big */
  323                 bio_put(bio);
  324                 return ret;
  325         }
  326 
  327         blk_queue_bounce(q, &rq->bio);
  328         rq->buffer = NULL;
  329         return 0;
  330 }
  331 EXPORT_SYMBOL(blk_rq_map_kern);
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FreeBSD/Linux Kernel Cross Reference sys/block/blk-map.c

FreeBSD/Linux Kernel Cross Reference
sys/block/blk-map.c
